Today, consciousness towards the environment is greater than in the past and containers must fulfill high safety demands, particularly for substances which are detrimental to the environment.
Nevertheless, such containers should be simple and easy to produce at low costs. Their handling should also be easy and simple, both when filling and sealing. Safety must be maintained when using fully automatic sealing as well as repeated sealing, even after numerous opening and closing operations. The closure means should even be able to resist outer and interior strain up to certain levels, so that leakage may be avoided with comparatively great security. Furthermore, the contents of such a container must be fed out in a simple and reliable way.
The previously known containers and their closure means do not fulfill these demands, at least not in combination.
Caps which are previously known in this technical field serve as sealing means for a cartridge or the like between its filling and use. When using the cartridge, the cap is normally removed and thrown away and has, therefore, no further function to fulfill.
Beyond this limited function, previously known caps often suffer from the drawback that they do not safely or sufficiently seal the container. Leakage may thus occur easily and frequently, and quite often full containers and adjacent containers, the contents of which have leaked out, must be thrown away, as it can be rather unpleasant to get ones hands and clothes soiled by the contents of the container.
Apart from the problem of possible leakage, the previously known caps are also hard to remove, particularly caps which are not designed as screwcaps. If the caps are designed as screwcaps, increased material thickness is required, as well as extra means to provide the cap with interior threads and extra means to provide the one cartridge end with outer threads.
Bamberger et al. discloses a cap for sealing one end of a container for fast food. This cap is furnished with a circumferential incision in the middle of an interior collar, which is torn apart when a plunger is pushed against the cap bottom, whereupon said bottom, with approximately half the axial length of the interior collar, serves as a plunger disk for feeding out fast food. Such a design shows drawbacks, as it may be very difficult, and quite remarkable forces may be needed, to make the collar crack within the area of the incision, where the collar continues on both sides in a straight way with the incision at a right angle in relation thereto. For this reason, as clearly revealed by FIG. 8, a need has occurred to increase substantially the thickness of the interior collar above the incision, in which way, obviously, the upper part of the interior collar and the outer collar should be prevented from following the plunger disk, in case the incision does not crack in spite of high pressure. Furthermore, this cap is not fixedly secured at the container in any way and pressures arising within the latter, e.g. when squeezing the container, would immediately lead to gliding of the cap away from the container. Even the feeding out of the contents of the container has to be regarded as disadvantageous, as that part of the interior collar which forms the plunger disk undergoes a change of shape from a position of rest with a shape converging towards the contents of the container, to a parallel position when plunger pressure is applied, whereby some of the contents of the container most probably will enter between the interior collar and the container wall, thus preventing a normal plunger function or leaking out backwards along the free edge of the interior collar. Finally, the remainder of the interior collar and the outer collar left behind on the container end are not secured in any way. These parts may be dislodged unintentionally at any time and thus constitute a waste problem. Such a closure means may, to a limited extent, be tolerated for harmless substances, e.g. fast food. It is, however, undoubtedly unsuitable for substances which are detrimental to the environment, such as lubricants and the like.